java并发编程之CountDownLatch

简介

CountDownLatch 犹如倒计时计数器，countDown（）计数器建议1，当等于0时所有等待者任务开始进行，可用于实现 一对多的指令通知场景，例如运动员赛跑的场景

public class MyThreadCountDownLatch {
    
    public static void main(String[] args) {
        ExecutorService threadPool = Executors.newCachedThreadPool();
        final CountDownLatch mainCdl = new CountDownLatch(1);//主裁判计数器（指令发射器）
        final CountDownLatch taskCdl = new CountDownLatch(3);//运动员计数器（结果反馈）
        for(int i=1;i<=3;i++){  //创建三个线程，模拟三个运动员
            Runnable task=new Runnable() {
                
                @Override
                public void run() {
                    try {
                        String threadName=Thread.currentThread().getName();
                        System.out.println("线程"+threadName +"准备接受指令");
                        mainCdl.await();
                        System.out.println("线程"+threadName +"收到指令");
                        Thread.sleep((long) (Math.random()*10000));  //真实以实际业务代码准
                        System.out.println("线程"+threadName +"回应处理结果");
                        taskCdl.countDown();//子线程发送结果指令（子线程计数器减1）
                    } catch (InterruptedException e) {
                        e.printStackTrace();
                    }
                }
            };
            threadPool.execute(task);  //启动线程
        }
        
        try {
            System.out.println("线程"+Thread.currentThread().getName() +"准备发送指令");
            Thread.sleep((long) (Math.random()*10000));
            mainCdl.countDown(); //主线发送信号（主线程计数器减1）
            System.out.println("线程"+Thread.currentThread().getName() +"等待处理结果");
            taskCdl.await();
            System.out.println("线程"+Thread.currentThread().getName() +"收到处理结果");
        } catch (InterruptedException e) {
            e.printStackTrace();
        }
        threadPool.shutdown();
        
    }

}